We are investigating factors affecting collateral ventilation between adjacent lobules within a lung lobe. Specifically, we plan to study the effects of a) sympathetic and parasympathetic innervation, b) mediators of the immune response, c) changes in local gas tensions, and d) changes in pulmonary vascular pressures and volume. In the previous year (1977-1978) we have begun studies of autonomic innervation of collateral resistance and the effects of histamine on collateral resistance. Vagal sectioning decreases collateral resistance in all dogs but interanimal variation is great. Similarly, stimulation of the distal ends of cut vagi increases collateral resistance to a varying degree. Variations in response to vagal section and stimulation are similar to vagal effects on peripheral airways where sympathetic tone appears to mask vagal effects. We therefore plan to investigate vagal effects on collaterals following administration of a Beta blocker (propranolol). We have shown that intravenous histamine administration initially increases collateral resistance, but at high histamine doses, resistance decreases as the dog's blood pressure falls. We feel the decrease in resistance may be associated with a sympathoadrenal discharge and plan to administer sympathetic blocking agents to test this hypothesis.